1. Field of the Invention
The present invention relates to a plasma display panel and a manufacture method thereof, and more particularly, to a plasma display panel and a manufacture method thereof in which when the plasma display panel is driven, a color mixture of emitted light can be prevented and a contrast characteristic can be improved.
2. Description of the Background Art
In general, plasma display panel (Hereinafter, referred to as “PDP”) includes a front substrate and a rear substrate formed of soda-lime glass, and a barrier rib defining one unit cell between the front substrate and the rear substrate. When inert gas such as He—Xe and He—Ne is discharged due to a high frequency voltage in each unit cell, vacuum ultraviolet rays are generated and phosphor is excited between the barrier ribs, thereby displaying an image.
FIG. 1 is a schematic perspective view illustrating a structure of a conventional plasma display panel.
As shown in FIG. 1, a plasma display panel (PDP) 100 includes a front substrate 10 and a rear substrate 20, which are spaced apart and engaged in parallel with each other. The front substrate 10 is a display surface on which the image is displayed. The rear substrate 20 is a rear surface. The front substrate 10 is formed at a lower side of the PDP. The front substrate 10 includes a pair of sustain electrodes 11 for sustaining light emission using a mutual discharge in one pixel. The sustain electrodes 11 are comprised of a transparent electrode 11a formed of indium-tin-oxide (ITO) and a bus electrode 11b formed of metal. The sustain electrodes 11 are covered with a dielectric layer 12a, which limits a discharge current and insulates the sustain electrodes. A passivation layer 13 is formed of oxide magnesium (MgO) on the dielectric layer 12a to facilitate a discharge. The rear substrate 20 includes stripe-type (or well-type) barrier ribs 21 and a plurality of address electrodes 22. The stripe-type (or well-type) barrier ribs 21 are arranged in parallel with one another to form a plurality of discharge spaces, that is, a plurality of cells. The plurality of address electrodes 22 are arranged in parallel with the barrier ribs 21 to perform an address discharge and generate vacuum ultraviolet rays at their intersection with the sustain electrodes 11. A dielectric layer 12b is formed on the address electrodes 22. Red (R), green (G), blue (B) phosphors 23 are coated on the dielectric layer 12b to emit a visible ray, thereby displaying the image in the address discharge. A method for expressing a gray level in the above constructed PDP is illustrated in FIG. 2.
FIG. 2 is a view illustrating a conventional method for expressing the gray level in the plasma display panel.
As shown in FIG. 2, the gray level is expressed by dividing one frame into several sub-fields each having a different number of light emission times. Each of the sub-fields is divided into a reset period for uniformly generating the discharge, an address period for selecting the discharge cell, and a sustain period for expressing the gray level depending on the number of discharge times. For example, when the image is displayed in 256 gray levels, a frame period (16.6 ms) corresponding to 1/60 second is divided into eight sub-fields (SF1 to SF8). Each of eight sub-fields is again divided into the reset period, the address period and the sustain period. The reset period and the address period are the same at each sub-field. The address discharge is generated by a voltage difference between the address electrode (data electrode) and the transparent electrode (scan electrode) to select the discharge cell. The sustain period is increased in a ratio of 2n (n=0,1,2,3,4,5,6,7) at each sub-field.
In general, in the PDP, the unit pixel is constituted of three kinds of sub-pixels emitting R, G, B lights. Each of the sub-pixels controls an amount of emitted light depending on the number of the sustain pulses, and visually juxtaposes and mixes the controlled lights, thereby expressing the color and the gray level.
FIGS. 3A through 3D are views illustrating various discharge cell structures in the conventional plasma display panel. FIG. 3A illustrates the discharge cell structure having a stripe-type barrier rib, FIG. 3B illustrates the discharge cell structure having a well-type barrier rib, FIG. 3C illustrates the discharge cell structure having a delta-type barrier rib, and FIG. 3D illustrates the discharge cell structure having a honey-type barrier rib.
As shown in FIGS. 3A through 3D, in sub-pixels 101a, 101b and 101c of the conventional PDP having the above discharge cell structure, a barrier rib 21 separates phosphors expressing each R, G, B color. The sub-pixels 101a, 101b and 101c constitute a unit pixel 101 with the barrier rib 21 functioning as a boundary. The unit pixel is arranged to form a predetermined shape with an adjacent unit pixel using the barrier rib 21 functioning as the boundary, to display the image.
In the PDP having the discharge cell structure, the barrier rib functions to prevent electrical and optical crosstalk between the sub-pixels or the unit pixels. The barrier rib is the most important element in controlling a display quality and a light emission efficiency of the PDP. In the conventional PDP, the barrier rib partitioning the unit pixel has the same width as the barrier rib functioning as the boundary between the R, G, B sub-pixels constituting the unit pixel. In the PDP where each unit pixel emits light and the emitted light is mixed and displayed, there is a drawback in that a color mixture characteristic depending on a color of the adjacent unit pixel is not good. In other words, since the barrier rib formed between the sub-pixels has the same width as the barrier rib formed between the unit pixels, when the PDP is driven, the color mixture characteristic between an inherent color of the unit pixel and the color of the adjacent unit pixel is deteriorated.
In the conventional PDP having the above discharge cell structure, a black matrix having a low reflectance is formed at the front substrate to separate the colors and decrease a reflectance between upper and lower unit pixels, thereby improving a contrast characteristic.
FIGS. 4A and 4B are views illustrating black matrix structures disposed at the front substrate in the conventional PDP having the stripe-type discharge cell structure or the well-type discharge cell structure.
Referring to FIGS. 4A and 4B, in the front substrate 10, a black matrix 13a is formed only in a traverse direction of the unit pixel 101. Such a black matrix structure has a good contrast characteristic due to color separation and reflectance reduction between the unit pixels 101 formed at upper and lower sides on the basis of the black matrix 13a. However, it is not so in left and right unit pixels. Accordingly, in the conventional rear substrate, the barrier rib 21 partitioning the unit pixels or the sub-pixels is formed of black-color material having the low reflectance to improve the contrast characteristic. However, such a black matrix structure has a drawback in that since the transparent front substrate is provided at a predetermined thickness between an upper end of the barrier rib and the exterior, the emitted light is not fully blocked between the unit pixels, thereby deteriorating the contrast characteristic.